How do I switch my weapon?

I have my starting weapon equipped, but I can't figure out how to use my bow now. If I press f, it says that I don't have a weapon to fire. I'm holding a bow and a quiver with arrows though. I assume that I need to equip it, but I can't figure out how. I also have a couple other weapons that I can use with A if they aren't in my backpack, but I'm not sure how to equip them either.